Balloon catheter with non-deployable stent having improved stability

ABSTRACT

An angioplasty catheter comprises a catheter body having a balloon or other radially expandable shell at its distal end. An external structure is carried over the shell and scores a stenosed region in a blood vessel when the balloon is inflated therein. The catheter has an attachment structure disposed between the catheter body and the balloon to accommodate foreshortening and rotation of the external structure as the balloon is expanded. The external structure may be part of a helical cage structure which floats over the balloon. Stabilizing struts are provided between at least some of the helical struts.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the field of medical devices, morespecifically to medical devices intended to treat stenoses in thevascular system.

Balloon dilatation (angioplasty) is a common medical procedure mainlydirected at revascularization of stenotic vessels by inserting acatheter having a dilatation balloon through the vascular system. Theballoon is inflated inside a stenosed region in a blood vessel in orderto apply radial pressure to the inner wall of the vessel and widen thestenosed region to enable better blood flow.

In many cases, the balloon dilatation procedure is immediately followedby a stenting procedure where a stent is placed to maintain vesselpatency following the angioplasty. Failure of the angioplasty balloon toproperly widen the stenotic vessel, however, may result in improperpositioning of the stent in the blood vessel. If a drug-eluting stent isused, its effectiveness may be impaired by such improper positioning andthe resulting restenosis rate may be higher. This is a result of severalfactors, including the presence of gaps between the stent and the vesselwall, calcified areas that were not treated properly by the balloon, andothers.

Conventional balloon angioplasty suffers from a number of othershortcomings as well. In some cases the balloon dilatation procedurecauses damage to the blood vessel due to aggressive balloon inflationthat may stretch the diseased vessel beyond its elastic limits. Suchover inflation may damage the vessel wall and lead to restenosis of thesection that was stretched by the balloon. In other cases, slippage ofthe balloon during the dilatation procedure may occur. This may resultin injury to the vessel wall surrounding the treated lesion. Oneprocedure in which slippage is likely to happen is during treatment ofin-stent restenosis, which at present is difficult to treat byangioplasty balloons. Fibrotic lesions are also hard to treat withconventional balloons, and elastic recoil is usually observed aftertreatment of these lesions. Many long lesions have fibrotic sectionsthat are difficult to treat using angioplasty balloons.

An additional problem associated with balloon angioplasty treatment hasbeen the “watermelon seed effect.” Angioplasty is carried out at veryhigh pressures, typically up to twenty atmospheres or higher, and theradially outward pressure of the balloon can cause axial displacement ofthe balloon in a manner similar to squeezing a watermelon seed with thefingers. Such axial displacement, of course, reduces the effectivenessof balloon dilatation. Another problem with conventional angioplastyballoon design has been deflation of the balloon. Even after theinflation medium is removed from a balloon, the deflated configurationwill have a width greater than the original folded configuration whichwas introduced to the vasculature. Such an increase in profile can makeremoval of the balloon difficult.

Atherectomy/Thrombectomy devices intended to remove plaque/thrombusmaterial may also include a structure that expands in a lesion while theplaque/thrombus removal mechanism is within this structure. The removedmaterial is either being stacked in the catheter or sucked out thru thecatheter. When the procedure is done, the expandable structure iscollapsed and the catheter removed. Foreign object removal devicesusually include a basket structure that needs to be expanded to collectthe object and then collapse for retrieval. Distal protection devicesusually include a basket structure that support a mesh that needs to beexpanded distal to the treated lesion to collect the loose objects andthen collapse for retrieval.

These devices usually include an elastic metallic material that needs tobe expanded in the vascular system to fulfill its task and afterwardscollapse to a small diameter to facilitate retrieval. The transitionbetween the collapsed (closed) configuration to the expanded (open)configuration can be done in two ways: the structure can be at anormally closed (collapsed) configuration in which force is applied tocause the structure to expand. In this case, the elastic recoil of thestructure will cause it to collapse back to closed configuration whenthe expanding force ceases. The structure may also be at a normally open(expanded) configuration in which a constraining element is forced overit to hold it down for the collapsed configuration (for example aconstraining tube). When this constraining element is removed thestructure is free to expand to the expanded (open) configuration. Thestructure material may also be non-elastic. In this case, the structurewill need to be forced to transit between both collapsed and expandedconfigurations.

One problem associated with conventional angioplasty expansion systemsis that the transition between the collapsed and expanded configurationsinvolves significant rotational and axial reaction forces. Thesereaction forces are applied by the structure on the catheter as a resultof the force applied by the catheter to expand or close the structure.Axial reaction forces are created due the foreshortening of thestructure during expansion. Rotational reaction forces (torques) arecreated when a non-longitudinal element is forced to expand/collapse.Since the catheters are usually less stiff than the structure, thesereaction forces may cause the structure to not expand or collapseproperly, or cause undesired deformation to the catheter itself.

For these reasons, it would be desirable to provide improved cutting orscoring balloon designs and methods for their use. In particular, itwould be desirable to provide cutting or scoring balloons which arehighly flexible over the length of the balloon structure, which readilypermit deflation and facilitate removal from the vasculature, and whichare effective in treating all forms of vascular stenoses, including butnot limited to treatment of highly calcified plaque regions of diseasedarteries, treatment of small vessels and/or vessel bifurcations thatwill not be stented, treatment of ostial lesions, and treatment ofin-stent restenosis (ISR). Moreover, it would be desirable if suchballoon structures and methods for their use could provide for improvedanchoring of the balloon during dilatation of the stenosed region.

It would further be desirable to minimize the reaction forces applied bythe external structure to the catheter, and at the same time be able tocontrol the expansion of the expandable structure. It would also bedesirable to adjust the compliance and improve the shape stability ofthe system in a predictable way without changing the materials orgeometry of the expandable structure. At least some of these objectiveswill be met with the inventions described hereinafter.

BRIEF SUMMARY OF THE INVENTION

The present invention provides improved apparatus and methods for thedilatation of stenosed regions in the vasculature. The stenosed regionswill often include areas of fibrotic, calcified, or otherwise hardenedplaque or other stenotic material of the type which can be difficult todilatate using conventional angioplasty balloons. The methods andapparatus will often find their greatest use in treatment of thearterial vasculature, including but not limited to the coronary arterialvasculature, but may also find use in treatment of the venous and/orperipheral vasculature, treatment of small vessels and/or vesselbifurcations that will not be stented, treatment of ostial lesions, andtreatment of ISR.

In a first aspect of the present invention a method of dilating astenosed region in a blood vessel is disclosed. The method includesintroducing a helical scoring structure having a distal end and aproximal end carried over a balloon, wherein the helical scoringstructure comprises a plurality of helical elements that longitudinallyextend from the distal end to the proximal end, and a plurality ofstabilizing struts spaced along the length of the helical scoringstructure and coupled to at least two adjacent helical elements,expanding the balloon to dilate the helical scoring structure within thestenosed region within the blood vessel, wherein the proximal end of thehelical scoring structure, which is free to move axially, moves distallyand the scoring structure shortens to accommodate such distal movementof the helical scoring structure as the balloon is expanded; holding theexpanded helical scoring structure in place to disrupt the stenoses; anddeflating the balloon causing the helical structure to collapse. Thestabilizing struts enhance the ability of the scoring structure tomaintain its desired shape.

The helical scoring structure means that the structure will be able toscore or cut stenotic material within a treated blood vessel along lineswhich are generally in a non-axial direction. For example, the scoringlines may be helical, serpentine, zig-zag, or may combine some axialcomponents together with such non-axial components. Usually, thenon-axial scoring pattern which is imparted will include scoringsegments which, when taken in total, circumscribe at least a majority ofand usually the entire inside wall of the blood vessel up to one time,preferably more than one time, usually more than two times, often atleast three times, more often at least four, five, six, or more times.It is believed that the resulting scoring patterns which circumscribethe inner wall of the vessel will provide improved results duringsubsequent balloon dilatation.

Usually the scoring structure will comprise at least one continuous,i.e., non-broken, scoring element having a length of at least 0.5 cm,more usually at least 1 cm, often at least 2 cm, usually at least 3 cm,and sometimes at least 4 cm or more. Alternatively, the scoringstructure may comprise a plurality of much smaller segments which may bearranged in a helical or other pattern over the balloon, typicallyhaving a length in the range from 0.1 cm to 2 cm, often being 0.5 cm orless, sometimes being 0.3 cm or less. Additionally, the scoringstructure elements may be adjoined to one another with one or morestabilizing struts. Rather than to extend along the entire length of thescoring structure, the stabilizing struts are configured to couple onescoring element with an adjacent scoring element.

In order to promote scoring of the blood vessel wall when the underlyingexpandable shell is expanded, the scoring structure will usually have avessel contact area which is 20% or less of the area of the expandableshell, usually being below 10%, and often being in the range from 1% to5% of the area of the expandable shell. The use of a shell having such arelatively small contact area increases the amount of force applied tothe vascular wall through the structure by expansion of the underlyingexpandable shell. The scoring structure can have a variety of particularconfigurations, often being in the form of a wire or slotted tube havinga circular, square, or other cross-sectional geometry. Preferably, thecomponents of the scoring structure will comprise a scoring edge, eitherin the form of a honed blade, a square shoulder, or the like. Apresently preferred scoring edge is electropolished and relativelysmall.

In a preferred embodiment, the scoring structure may be formed as aseparate expandable cage which is positioned over the expandable shellof the catheter. The cage will usually have a collar or other attachmentstructure at each end for placement on the catheter body on either sideof the expandable shell. A collar may be a simple tube, and otherattachment structures will usually be crimpable or otherwisemechanically attachable to the catheter body, such as a serpentine orother ring structure. The attachment structures on the cage may beattached at both ends to the catheter body, but will more usually beattached at only a single end with the other end being allowed to floatfreely. Such freedom allows the scoring structure to shorten as thestructure is expanded on the expandable shell. In certain embodiments,both ends of the scoring structure will be fixed to the catheter body,but at least one of the attachment structures will have a spring orother compliant attachment component which provides an axial extensionas the center of the scoring structure foreshortens.

In many cases, since the scoring elements are non-axial, there aretorques induced during the expansion of the balloon and the shorteningof the scoring structure. These torques may be high, and if one end ofthe scoring structure is constrained from rotation, the scoring elementwill not expand properly. The final expanded configuration of thescoring element is achieved via shortening and rotation.

In a preferred embodiment, both sides of the scoring element are fixedto the catheter, but at least one side will have a compliant structurewhich will provide axial tension and at the same time will allow thescoring element to rotate to its final configuration.

In some cases both ends of the scoring element are fixed and theshortening is achieved by deformation of the wire. For example, the wirecan have a secondary structure which permits elongation (e.g., it may bea coiled filament) or can be formed from a material which permitselongation, e.g., nitinol. The scoring element can be attached in bothends, in a way that will allow rotation. In the case were the torquesare low (depending on the design of the scoring element) there is noneed for rotation and the torque can be absorbed either be the scoringelement or by the catheter.

In all cases, the scoring structure is preferably composed of an elasticmaterial, more preferably a super elastic material, such as nitinol. Thescoring structure is thus elastically expanded over the expandableshell, typically an inflatable balloon similar to a conventionalangioplasty balloon. Upon deflation, the scoring structure willelastically close to its original non-expanded configuration, thushelping to close and contain the balloon or other expandable shell.

In some cases the scoring element will be a combination of more than onematerial. In one case the scoring element can be made from nitinol andparts of it can be made from stainless steel. In other cases the scoringelement can be made of stainless steel or nitinol and part of it can bemade from polymer to allow high deformations.

In other preferred embodiments, the assembly of the shell and thescoring structure will be sufficiently flexible to permit passagethrough tortuous regions of the vasculature, e.g., being capable ofbending at radius of 10 mm or below when advanced through 45°, 90°, orhigher bends in the coronary vasculature. Usually, the scoring structurewill comprise one or more scoring elements, wherein less than 70% of thecumulative length of the scoring element is aligned axially on the shellwhen expanded, preferably being less than 50% of the cumulative length,and more preferably being less than 25% of the cumulative length. Inother instances, the scoring structure may comprise one or more scoringelements, wherein the cumulative length of the scoring element includesa non-axial component of at least 10 mm, preferably at least 12 mm, andmore preferably 36 mm. Preferably, at least some of the scoring elementswill have scoring edges which are oriented radially outwardly along atleast a major portion of their lengths at all times during inflation anddeflation and while inflated. By “radially outward,” it is meant that anedge or shoulder of the element will be oriented to score the stenoticmaterial or the interior wall of the treated vessel, particularly as theshell is being inflated.

The scoring elements will usually, but not necessarily, have a scoringedge formed over at least a portion of their lengths. A “scoring edge”may comprise a rounded or square such as found on a wire. The scoringelements will concentrate the radially outward force of the balloon tocause scoring or other disruption of the plaque or other stenoticmaterial being treated.

In a second aspect of the present invention, the scoring cathetercomprises a catheter body and a radially expandable shell, generally asset forth above. The scoring catheter includes a helical scoringstructure having a distal end and a proximal end carried over a balloon,wherein the helical scoring structure is configured to radially expandin response to balloon inflation and further comprises a plurality ofhelical elements that longitudinally extend from the distal end to theproximal end, and a plurality of stabilizing struts spaced along thelength of the helical scoring structure and coupled to at least twoadjacent helical elements, and a catheter body configured to carry thehelical scoring structure at a distal end.

In a third aspect of the present invention, an expansible scoring cageadapted to be carried over a balloon of a balloon catheter is disclosed.The expansible scoring cage includes an assembly having a plurality ofhelical scoring elements, wherein said assembly is normally in aradially collapsed configuration and expansible over a balloon to aradially expanded configuration, wherein the assembly returns to itsradially collapsed configuration when the balloon is deflated; furtherwherein the plurality of helical scoring elements are coupled to eachother via a plurality of stabilizing struts along the longitudinallength of the helical scoring elements.

An elongated scoring structure is carried over the shell, and theassembly of the shell and the scoring structure will be highly flexibleto facilitate introduction over a guide wire, preferably beingsufficiently flexible when unexpanded so that it can be bent at an angleof at least 90°, preferably 180°, at a radius of 1 cm without kinking orotherwise being damaged. Such flexibility can be determined, forexample, by providing a solid cylinder having a radius of 1 cm andconforming the assembly of the scoring structure and expandable shellover the cylinder. Alternatively, the assembly can be advanced over aguide wire or similar element having a 180° one centimeter radius bend.In either case, if the assembly bends without kinking or other damage,it meets the requirement described above. Other specific features inthis further embodiment of the catheters of the present invention are asdescribed above in connection with the prior embodiments.

In still another aspect of the apparatus of the present invention, anexpandable scoring cage is adapted to be carried over a balloon of aballoon catheter. The scoring cage comprises an assembly of one or moreelongate elastic scoring elements arranged in a non-axial pattern. Asdefined above, the non-axial pattern may comprise both axial andnon-axial segments. The assembly is normally in a radially collapsedconfiguration and is expandable over a balloon to a radially expandedconfiguration. After the balloon is deflated, the assembly returns to aradially collapsed configuration, preferably being assisted by theelastic nature of the scoring cage and a series of stabilizing struts.Advantageously, the scoring cage with stabilizing struts will enhanceuniform expansion of the underlying balloon or other expandable shelland will inhibit “dog boning” where an angioplasty balloon tends to overinflate at each end, increasing the risk of vessel dissection. Thescoring elements will be adapted to score hardened stenotic material,such as plaque or fibrotic material, when expanded by the balloon in ablood vessel lumen. The scoring cage may be adapted to mount over theballoon with either or both ends affixed to the balloon, generally asdescribed above in connection with prior embodiments. Preferredgeometries for the scoring elements include those which circumscribe theballoon, those which are arranged helically over the balloon, thosewhich are arranged in a serpentine pattern over balloon and the like.

In yet another aspect of the present invention, a method for dilatatinga stenosed region in a blood vessel comprises radially expanding a shellwhich carries a scoring structure. The scoring structure scores anddilates the stenosed region and includes one or more non-axial scoringelements arranged to impart a circumscribing score pattern about theinner wall of the blood vessel as the shell is expanded. The stenosedregion is typically characterized by the presence of calcified plaque,fibrotic plaque, or other hardened stenotic material which is preferablyscored prior to dilatation. Preferably, the scoring structure will notbe moved in an axial direction while engaged against the stenosedregion, and the scoring structure may optionally be free from axiallyscoring elements.

In still another aspect of the present invention, an angioplastycatheter comprises a catheter body and a radially expandable shell nearthe distal end of the catheter body. An external structure, such as ascoring structure or cutting structure, is carried over but unattachedto the shell. The catheter further comprises an attachment structurehaving a proximal end and a distal end attached to the scoringstructure, wherein the attachment structure is sufficiently sized andcompliant to accommodate reaction forces or geometrical changes producedby the scoring structure as it is expanded by the shell. Generally, atleast a portion of said scoring structure is arranged helically over theshell. However, the scoring structure may comprise numerous differentconfigurations as described above.

In one aspect of the present invention, the proximal end of theattachment structure is fixed to the catheter body and the distal end ofthe attachment structure is secured to the proximal end of the scoringstructure. In all cases, the attachment structure is capable of axiallyand rotationally extending to accommodate foreshortening of the scoringstructure as the shell is expanded.

It is understood that other embodiments of the specific teachings hereinwill become readily apparent to those skilled in the art from thefollowing detailed description, wherein it is shown and described onlyseveral embodiments of the teachings by way of illustration. As will berealized, the subject matter of the teachings herein is capable of otherand different embodiments and its several details are capable ofmodification in various other respects, all without departing from thespirit and scope of these teachings. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 1A, 1B, and 1C are schematic illustrations of the balloonscoring structure embodiment in accordance with an embodiment of theinvention.

FIG. 2 is a schematic illustration of an exemplary helical scoringstructure embodiment in accordance with embodiments of the invention.

FIGS. 3, 3A, and 3B illustrate self-closing cage configurations inaccordance with the embodiments of the invention.

FIG. 4 illustrates an alternative embodiment of a helical scoringstructure comprising serpentine and zigzag structures for mounting ontoa balloon catheter.

FIG. 5 illustrates a first of the serpentine mounting elements of thescoring structure of FIG. 4.

FIG. 6 illustrates a second of the serpentine mounting elements of thescoring structure of FIG. 4.

FIG. 7 illustrates an alternative mounting structure for a helical orother scoring structure.

FIG. 8 illustrates the mounting structure of FIG. 7 shown in arolled-out configuration.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionwill be described. For purposes of explanation, specific configurationsand details are set forth in order to provide a thorough understandingof the present invention. However, it will also be apparent to oneskilled in the art that the present invention may be practiced withoutthe specific details presented herein. Furthermore, well-known featuresmay be omitted or simplified in order not to obscure the presentinvention.

Embodiments of the present invention relate to a device forrevascularization of stenotic vessels and specifically to a ballooncatheter having external scoring elements. The dilatation devicecomprises a conventional dilatation balloon such as a polymeric balloonand a helical scoring structure. Alternatively, other scoringconfigurations may be mounted on the balloon catheter without departingfrom the teachings disclosed herein.

Reference is now made to FIGS. 1, 1A, and 1B, which are schematicillustrations of a dilatation device 10 in accordance with embodimentsdescribed herein. The dilatation device 10 includes a dilatation balloon12, which may be any conventional angioplasty balloon such as commonlyused by interventional cardiologists or radiologists, and a helicalassembly 14 mounted over or attached to the dilatation balloon 12. Thehelical assembly 14 also includes at least one stabilizing strut 11 thatcouples one longitudinal strut to an adjacent longitudinal strut, asdepicted in FIG. 1. Preferably, the helical assembly 14 will incorporatea series of stabilizing struts that extend about the longitudinal lengthof the helical assembly 14. For added stability, the stabilizing struts11 may be spaced evenly or unevenly along the longitudinal axis of thehelical assembly 14. Helical unit 14 may be attached at 17 and 18 to thecatheter shaft proximate to proximal and distal ends of the balloon 12by collar-like attachments 15 and 16 (See FIG. 2).

The stabilizing struts 11 may additionally provide for the long scoringelements of the helical assembly 14 to deploy in an evenly spaced mannerduring balloon inflation to various pressures. The stabilizing struts 11may also minimize the possibility that the scoring element struts orwires will bunch together during device operation, and, still further,assist with keeping the scoring elements from lifting from the balloonsurface at its deflated state, thereby facilitating device pull back. Inother words, as will be appreciated by one of ordinary skill, theincorporation of stabilizing struts 11 may create a stable supportstructure between the otherwise independently floating struts (See FIG.2). The stabilizing strut(s) 11 may have at least one bend along itspath extending from one scoring element to an adjacent scoringelement—or the same scoring element in the single wire embodiment. Theat least one bend, preferably at least two, would facilitate maintainingthe narrow profile of the collapsed helical structure for unobstructedremoval of the catheter from the body lumen post-treatment. Moreover,the points at which the stabilizing strut 11 meets the two adjacenthelical elements may be typically offset along the longitudinal axis toaccommodate the expanded and collapsed configurations without having anyhelical scoring elements or stabilizing struts detach or otherwise strayfrom the scoring structure's profile.

Further, the compliance of the balloon and the scoring element(s) shouldbe chosen to assure uniform expansion of the balloon substantially freefrom “dog-boning” as the combined structure expands within a lesion. Ifa compliant or a semi-compliant balloon is used and the compliance ofthe scoring element was not matched to comply with the properties of theballoon, the expansion of the balloon-scoring element system will not beuniform. This non-uniformity may impair the efficacy of the scoringcatheter and, in some cases, may result in poor performance. Forexample, under given pressure, certain parts of the balloon 12 will beable to expand while other parts will be constrained by excessiveresistance of the scoring elements.

The helical unit or assembly 14 is typically made of nitinol. Helicalunit 14 may be made of other metals such stainless steel,cobalt-chromium alloy, titanium, and the like. Alternatively, helicalunit 14 may be a polymeric helix, or made of another elastic material.Helical unit 14 may be attached at its proximal and distal ends to thecatheter shaft proximate to the proximal end 17 and distal end 18 ofdilatation balloon 12. Alternatively, helical unit 14 may be attached tothe catheter shaft proximate to the distal end and/or the proximal endof dilatation balloon 12 by collar-like attachment elements 15 and 16.(See FIG. 2). Still further, one or both collar-like attachments 15 and16 may be free to slide on the catheter shaft. Spring or other compliantelements may be alternatively or additionally provided as part of theattachment elements to accommodate shortening of the helical unit 14 asit is expanded.

Dilatation device 10 is inserted into the vascular system, for example,using a conventional catheter procedure, to a region of stenoticmaterial 22 of blood vessel 20. (The term “stenotic” is used herein torefer to the vascular lesion, e.g., the narrowed portion of the vesselthat the balloon is meant to open.) At the stenotic area 22, thedilatation balloon 12 is inflated, for example, by liquid flow into theballoon. Helical unit 14 widens on the inflated dilatation balloon 12.On inflation, the dilatation balloon 12 together with the helical unit14 is pressed against the walls of blood vessel 20 as shown in FIG. 1B.

Reference is now made to FIG. 1C, illustrating blood vessel 20 after thedeflation of dilatation balloon 12. Helical unit 14 narrows whendeflating the dilatation balloon 12, thus the dilatation device 10 isnarrowed and may be readily retrieved from blood vessel 20. Thedeflation profile of the balloon 10 is low and mainly circular. Thestenotic material 22 in blood vessel 20 is pressed against blood vessel20 walls to widen the available lumen and enhance blood flow. Thepressing of helical unit 14 against the walls of blood vessel 20 causesscoring 23 in the stenotic area.

Helical unit 14 may be pushed outwardly by the inflation of the balloon12, and is stretched by the inflation of the balloon. When the balloonis deflated, helical unit 14 assists in the deflation by its elasticrecoil. This active deflation is faster and also leads to a low profileof the deflated balloon. The balloon 12 is disposed within the helicalunit 14, which returns to its pre-inflated shape and forces the balloonto gain a low radial profile.

In another embodiment of the invention, dilatation device 10 may carry astent. The stent can be crimped over the helical unit 14. In this way,the helical unit 14 can push the stent against hard areas of the lesion,enabling proper positioning of the stent against the vessel wall, evenin hard-calcified lesions without pre-dilation.

Reference is now made to FIG. 2, illustrating the helical unit 14 inaccordance with embodiments of the invention. Helical unit 14 istypically made of nitinol. Helical unit 14 includes but is not limitedto three wires 19 that are attached to collars 15 and 16 at the proximalend and distal end, respectively. As depicted in connection with FIG. 2,stabilizing struts 11 are coupled between adjacent scoring elements, inthis embodiment, wires 19. Alternatively, the scoring structure maycomprise wires of other elements attached directly to the balloonmaterial or close to the balloon ends.

Wires 19 are attached between collars 15 and 16. The diameter of thewires is typically in the range of 0.05 mm to 0.5 mm. Alternatively, acage (for example a metallic cage made of a slotted tube) can be used inseveral configurations that allow local stress concentrations. The sizeand shape of the cross section of the cage elements or the cross sectionof the wires can vary. The cross section can be a circle, rectangle,triangle, or other shape.

In alternative embodiments, the wires 19 may comprise short segmentsthat are attached to the balloon 12. In further alternative embodimentsof the invention, the helical unit 14 may be glued, thermally bonded,fused, or mechanically attached at one or both ends to the dilatationballoon 12. In yet another embodiment, a scoring structure may comprisewires that are attached to the dilatation balloon 12 in a helicalconfiguration or other configuration. The wires may be thermallyattached to the balloon 12, glued, mechanically attached, or the like.In still another embodiment, a scoring structure comprises wire or cageelements that are not parallel to the longitudinal axis of the balloon12 so that the combination of the scoring structure 19 and the balloon12 remains flexible.

In additional embodiments, the combination of dilatation balloon 12 andscoring structure scores the lesion and provides better vesselpreparation for drug eluting stents by allowing better positioning ofthe stent against the vessel wall and diffusion of the drug through thescores in the lesion. In these embodiments, the balloon can be used as aplatform to carry drugs to the lesion where scoring of the lesion canenhance delivery of the drug to the vessel wall. The balloon may then beused for local drug delivery by embedding drug capsules, drug containingpolymer, and the like, through the stenotic material and into the vesselwall.

The scoring structures may be attached directly to the balloons or othershells, in some cases being embedded in the balloon material, but willmore usually be formed as separate cage structures which are positionedover the balloon and attached to the catheter through attachmentelements on either side of the balloon. The expandable cages may beformed using conventional medical device fabrication techniques, such asthose used for fabricating stents, such as laser cutting of hypotube andother tubular structures, EDM forming of hypotubes and tubes, welding ofwires and other components and the like.

Typically, such expandable shell structures will comprise the attachmentelements and an intermediate scoring section between the attachmentelements. As illustrated in the embodiments above, the attachmentelements may be simple cylindrical or tube structures which circumscribethe catheter body on either side of the balloon or other expandableshell. The simple tube structures may float over the catheter body,i.e., be unattached, or may be fixed to the catheter body. A number ofalternative embodiments for the attachment elements will be described inconnection with the embodiments below.

The intermediate scoring sections may also have a variety ofconfigurations where at least some of the scoring elements willtypically be disposed in a non-axial configuration, i.e., in a directionwhich is not parallel to the axial direction of the expandable cage. Apreferred configuration for the intermediate scoring section comprisesone or more helical elements, generally as illustrated in the priorembodiments. Other exemplary configurations are set forth in theembodiments described below.

Reference is now made to FIG. 3 that shows a scoring structure in theform of a single wire 24 wrapped around a dilatation balloon 12 in ahelical configuration. Additionally, with respect to the single wire 24embodiment, stabilizing struts 11 may be disposed either randomly orevenly throughout the entire length of the helical unit 14 for addedstability in the expansion and collapse of the helical scoring unit. Asdepicted by the spaces in FIGS. 3, 3A, and 3B, the helical assembly maybe of any longitudinal length appropriate for the treatment site. Theincorporation of stabilizing struts 11, however, may be most beneficialon either a relatively long helical assembly, e.g., any scoringstructure longer than 50 mm, or a relatively short helical assembly thatis designed to accommodate a balloon having a large diameter. Forexample, long scoring elements may be preferable when used tospecifically address long, diffuse lesions of the femoro-poplitealarteries where a 100-300 mm scoring structure may be desirable—leadingto fewer inflations and reduced procedure times. Conversely, shortscoring elements on a 20-40 mm catheter may be preferable when used totreat a lesion within a large diameter vessel, requiring a balloonhaving a diameter of between 18-24 mm. With the addition of stabilizingstruts to the helical assembly, the design and manufacture of lengthyand/or large diameter catheters becomes feasible.

Although the illustrated structure of an elastic metal, helicalstructure 10 may be preferred as it effectively maintains equalcircumferential spacing of the scoring elements 24 as the shell 12 isinflated or otherwise expanded, other helical designs may be employed,such as those having a plurality of helical scoring elements, asillustrated in FIGS. 3A and 3B. In FIG. 3A, a cage 10 comprising sixhelical scoring elements 24, and a series of stabilizing struts 11, isdisposed over an inflatable balloon 12. The construction of the catheterwhich carries balloon 12 and cage 10 will generally be the same as thatdescribed with respect to the foregoing description. FIG. 3B alsodescribes an expansible cage 10 having a plurality of helical scoringelements 24, and a plurality of stabilizing struts 11, where theprincipal difference is that cage 10 includes twelve scoring elements incontrast to six scoring elements of FIG. 3A.

In other embodiments, the scoring structure of the present invention canhave a non-helical configuration. Any design of scoring structure thatcan accommodate an increase in the diameter of the balloon 12 uponinflation, and return to its configuration when the balloon is deflated,is an appropriate design useful in the invention. At least a portion ofthe scoring elements will not be parallel to the longitudinal axis ofthe balloon catheter to enhance flexibility and improve scoring.

Referring now to FIGS. 4-6, alternative attachment elements are shown onan embodiment of an expandable scoring cage 140 comprising three helicalscoring elements 142, supported by a plurality of stabilizing struts 11,which make up the intermediate scoring section. A first attachmentelement 146 comprises a single serpentine ring, as best illustrated inFIG. 5 while a second attachment element 148 comprises a pair of tandemserpentine rings 150 and 152, as best illustrated in FIG. 6. The use ofsuch serpentine attachment structures is beneficial since it permitscrimping of either or both of the structures onto the catheter body inorder to fix either or both ends of the structure thereto. Usually, thesingle serpentine attachment structure 146 will be affixed to thecatheter body while the double serpentine structure will be left free toallow movement of that end of the scoring cage to accommodate radialexpansion of the underlying balloon.

Referring now to FIGS. 7 and 8, a further alternative embodiment of anattachment element useful in the scoring cages of the present inventionis illustrated. Attachment element 180 includes a pair of serpentinerings 182 and 184, generally as shown in FIG. 7, in combination with acoil spring structure 186 located between said rings 182 and 184. Thecoil spring structure 186 includes but is not limited to three nestedcoil springs 190, each joining one of the bend structures 192 and 194 onthe serpentine rings 182 and 184, respectively. The spring likestructure can take on many forms that allow for linear and rotationalmovement during expansion and retraction of the scoring cage. Thestructure of the spring structure and adjacent serpentine rings can beunderstood with reference to the rolled-out configuration shown in FIG.8.

The attachment structure 180 is advantageous since it permits a fixedattachment of the outermost ring 182 to the underlying catheter bodywhile the inner ring 184 remains floating and expansion and contractionof the intermediate scoring section, comprising helical elements 196, isaccommodated by the coil spring structure 186. Since the scoring cage isfixed to the catheter, any risk of loss or slippage from the balloon isreduced while sufficient compliance is provided to easily accommodateradial expansion of the intermediate scoring section. By attaching thestructures 180 at at least one, and preferably both ends of the scoringcage, the risk of interference with a stent is reduced.

In some embodiments, collars, such as those shown in FIGS. 1 and 2, orattachment elements, such as those shown in FIGS. 4-6, may comprise aflexible material that allows the collar or attachment element to expandwhile being mounted over the balloon catheter and then be collapsed tothe diameter of the catheter. The expandability of the collars and/orattachment elements may be achieved by a compliant memory material suchas nitinol or a polymer, or by use of a flexible serpentine design asshown in FIGS. 4-6. Where collars are used, the collar may be shaped orhave a slit down the circumference (not shown) so that the collar may beexpanded during mounting over the balloon. Alternatively, the collar maybe oversized to accommodate the balloon diameter mounting, and thencrimped down to secure the secure the scoring structure to the catheterbody.

The embodiments of FIGS. 7-8 comprise a spring-like element 186 toaccommodate axial shortening of the scoring structure upon radialexpansion. It will be appreciated that other metal and non-metal axiallyextensible structures could also be used in such attachment structures.For example, elastic polymeric tubes could be attached at one end to thescoring structures and at another end to the catheter body (or to aring, collar or other structure which in turn is fixed to the catheterbody).

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the teachingsherein. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the teachings disclosed herein. Thus, the scope ofthe disclosures herein is not intended to be limited to the embodimentsshown and described, but is to be accorded the widest scope consistentwith the general principles and novel features disclosed herein.

What is claimed is:
 1. A method of dilating a stenosed region in a bloodvessel, the method comprising the steps of: introducing an angioplastycatheter having a body and a helical scoring structure having a distalend and a proximal end carried over a balloon on the body, wherein thehelical scoring structure comprises a plurality of helical elements thatlongitudinally extend from the distal end to the proximal end, whereinthe plurality of helical elements are coupled together at the distal endand the proximal end, and a plurality of stabilizing struts, whereineach of the stabilizing struts is spaced between and coupled to at leasttwo adjacent helical elements, expanding the balloon to dilate thehelical scoring structure within the stenosed region within the bloodvessel, wherein the proximal end of the helical scoring structure movesdistally and the helical scoring structure shortens to accommodate suchdistal movement of the proximal and of the helical scoring structure asthe balloon is expanded; holding the expanded helical scoring structurein place to disrupt the stenosis; and deflating the balloon causing thehelical structure to collapse.
 2. The method of claim 1 wherein thehelical scoring structure accommodates rotation of the plurality ofhelical elements as the balloon is expanded.
 3. The method of claim 2wherein the plurality of stabilizing struts are evenly spaced along thelength of the helical scoring structure.
 4. The method of claim 3wherein the helical scoring structure comprises a metal.
 5. The methodof claim 4 wherein the helical scoring structure is unattached to theballoon and the distal end and proximal end of the scoring structure arecoupled to the catheter body.
 6. The method of claim 4 wherein thehelical scoring structure comprises nitinol.
 7. The method of claim 5wherein at least one of the distal end and the proximal end of thehelical scoring structure is capable of moving axially.
 8. The method ofclaim 1 wherein said scoring structure has a length in the range ofabout 50 mm to about 300 mm.
 9. The method of claim 1 wherein saidballoon is capable of expanding to a diameter of about 18 mm to about 24mm.
 10. The method of claim 1 wherein said scoring structure has alength of at least about 50 mm.